Hi,
As was explained in http://issues.apache.org/scarab/issues/id/TRQS318,
LargeSelect has a very poor performance for databases with no native
limit/offset. I lookead at the code myself and also am of the opinion that
using LargesSelect makes no sense if the db does not support native
limit/offset.
Therefore I am inclined to follow the proposed solution and throw an
exception in the constructor of LargeSelect if the chosen DB does not
support native limit and offset. The code would look loke:
private void init(Criteria criteria, int pageSize, int
memoryLimitPages)
throws IllegalArgumentException
{
...
{
String dbName = criteria.getDbName();
if (dbName == null)
{
dbName = Torque.getDefaultDB();
}
if (dbName == null)
{
throw new RuntimeException(
"Torque is not initialized yet");
}
DB db;
try
{
db = Torque.getDB(dbName);
}
catch (TorqueException e)
{
throw new RuntimeException(
"cannot retieve Database for DB name " + dbName);
}
if (db.getLimitStyle() == DB.LIMIT_STYLE_NONE)
{
throw new IllegalArgumentException(
"criteria must have a db which supports "
+ "native Limit and Offset");
}
}
...
Are there any objections ? Is everybody ok with throwing a
RuntimeException, or would it be better to add the TorqueException to the
throws clause, possibly breaking people's code because TorqueException is
not caught ?
I would also guess that the problems with databases which do not support
native limit/offset have lead to the exclusion of the LargeSelectTest from
the runtimetest. Does anybody object to include the LargeSelectTest
and print an error but not execute the test if the database dose not
support native limit/offset ? Sample code would be
public class LargeSelectTest extends BaseRuntimeTestCase
{
....
public void testLargeSelect() throws TorqueException
{
if (Torque.getDB(Torque.getDefaultDB()).getLimitStyle()
== DB.LIMIT_STYLE_NONE)
{
log.error("LargeSelect is known not to work for databases "
+ "which do not support native limit/offset");
return;
}
....
If one adds this, the LargeSelectTest also runs for hsqldb which does not
support native limit/offset.
Thomas
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
